A Practical Prefab Dormer, Images 29-36

Rake Overhang: It's easier to cut curves in OSB than in 2-by lumber, so we made the radiused barge rafters out of 3/4-inch AdvanTech sheathing, using the gable end as a pattern. Before installing the rake ladder, we traced the profile onto a piece of Azek 1x12 PVC trim that we would install later.

Rake Overhang: We made the ladder with 2x6 blocks, and installed it so that there's a butt joint rather than a miter at the ridge, which would give better nailing for the PVC trim and help prevent it from opening up.

Countdown: While the dormer was still inside, we trimmed out the gables and eaves with Azek, then sheathed the roof with 3/ 8-inch CDX plywood. We first hand-nailed to get the sheathing to conform to the curve, then finished up with staples. To make it easier to nail the valley plates to the roof deck, we left a couple of small sections of the sheathing tacked.

Countdown: Next we cut out the roof opening and placed some framing members around the edge to help us accurately position the dormer. We were ready for liftoff.

Installation: We slid the dormer out through a large ground-floor opening, attached it with straps to the lift, and hoisted it up.

Installation: It took a single carpenter only a few minutes to fasten the dormer.

Installation: The carpenter filled in the sheathing.

Installation: The finished dormer in place.

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